The present invention relates to tracheal tubes and, more particularly, to tracheal tubes of the type embodying a cuff for effecting a seal between the tube and a trachea.
The primary object of the present invention is to afford a novel tracheal tube.
Another object is to enable an effective seal between a tracheal tube and a trachea to be effected in a novel and expeditious manner.
A further object of the present invention is to afford a novel tracheal tube which is particularly useful during high positive pressure ventilation of a respiratory tract.
Tracheal tubes, as that term is used herein, may be of different types, such as, for example, orotracheal tubes, nasotracheal tubes and tracheostomy tubes. Also, such tubes may be flexible, the main body portion thereof being made of flexible material such as, for example, rubber or a suitable plastic material such as, for example, polyvinylchloride, or the like, or they may be stiff or rigid, being made of material such as stainless steel, or the like, the latter type of tubes being primarily useful as tracheostomy tubes. The present invention is intended for use in the construction of all such tracheal tubes.
As is well known in the art, tracheal tubes are commonly inserted into a person's trachea for various purposes, such as, for example, to enable the person to breathe, or to enable intermittent positive pressure ventilation of the respiratory tract to be carried out. An important object of the present invention is to afford a novel tracheal tube which is particularly well adapted for the latter aforementioned use, especially where high ventilating pressures are utilized.
Often, it is highly important, particularly in such instances as when positive pressure ventilation of the respiratory tract is to be carried out, that an airtight or substantially airtight seal be provided between the tracheal tube and the trachea. Heretofore, various attempts have been made to effect such seals between tracheal tubes and the trachea, such as, for example, by using large tubes which completely fill the trachea, or using cuffs on the tubes, which are expandable outwardly into engagement with the inner wall of the trachea.
Cuffed tracheal tubes heretofore known in the art, have been of two types. In one of those types, cuffs in the form of elastic diaphragms or tubes, made of elastic material, such as, for example, latex rubber, have been mounted on the main tube in sealed surrounding relation thereto, with the cuff normally, and when being inserted into the trachea, being in uninflated or deflated condition. With such devices, after the intubation device has been inserted into the trachea, the cuff is inflated like a balloon, by feeding air or other working fluid thereinto at a positive pressure to thereby expand the cuff into engagement with the inner wall of the trachea. However, it has been found that such devices have several inherent disadvantages, the primary disadvantage being that they commonly cause injury to the trachea, causing lesions such as tracheal stenosis, tracheal malacia and localized erosion, and the like, particularly if it is necessary for the tube to remain in the trachea for prolonged periods of time.
The other type of cuffed tracheal tubes heretofore known in the art is of a type such as that shown in U.S. Pat. No. 3,640,282, issued to Jack M. Kamen and Carolyn J. Wilkinson, on Feb. 8, 1972, wherein the cuff embodies a cover filled with resilient material, with the cuff normally being disposed in expanded position and being collapsed by applying a vacuum thereto during insertion of removal of the tube into or from the trachea, respectively. It is with respect to this latter type of tracheal tube to which the present invention pertains.
Current techniques of mechanical ventilation of the respiratory tract often employ relatively high positive air pressure. This pressure is highest at the peak of the inspiratory phase and lowest at the termination of the expiratory phase.
The human trachea is elastic. The degree of elasticity varies and is dependent upon a number of factors, the majority of which cannot or should not be controlled during such mechanical ventilation.
The two aforementioned factors, namely, current mechanical ventilation techniques and tracheal elasticity create a problem for cuffed endotrachael tubes to overcome. If the cuff is of the aforementioned air-filled type, the volume of air required to "no leak" ventilation at peak inspiratory airway pressure exceeds the volume of air needed in the cuff during expiration. The result in many instances is a progressive stretching of the trachea with ultimate tracheal injury.
On the other hand, when the cuff on the tracheal tube is of the expandable-material filled type, such as, for example, th type disclosed in the aforementioned Kamen and Wilkinson U.S. Pat. No. 3,640,282, the cuff contents exert prgressively less force against the tracheal wall as the elastic trachea's volume is expanded at peak inspiratory pressure. If this expansion of the elastic trachea is of sufficient magnitude, the result may be an inadequate seal between the cuff and the trachea. It is an important object of the present invention to enable this danger to be overcome in a novel and expeditious manner.
Heretofore, in an attempt to insure the proper seal between the trachea and a cuffed tracheal tube during mechanical ventilation and to minimize or prevent tracheal injury, cuff inflator machines have been used. These machines either attempt to vary the cuff volume and pressure synchronously with a companion ventilating machine or to maintain a constant cuff pressure while varying the cuff volume during the changing requirements of a complete inspiration/expiration cycle. These machines have several disadvantages, among which are that they are expensive and are subject to the maintenance and calibration problems inherent to precise machinery. It is an important object of the present invention to enable the aforementioned seal-maintenance problem to be overcome in an inexpensive, novel and expeditious manner.
Another object of the present invention is to afford a novel tracheal tube of the aforementioned normally-expanded type, wherein the pressure of the cuff against the tracheal wall, and the cuff volume during mechanical ventilation of a respiratory tract, may be controlled in a novel and expeditious manner.
Another object of the present invention is to afford a novel tracheal tube which is practical and efficient in operation, and which may be readily and economically produced commercially.
A still further object of the present invention is that the method prevents the peak pressure in the cuff from exceeding peak airway pressure.
Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment of the present invention and the principles thereof and what I now consider to be the best mode in which I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.